Cartilage tissue forms the nose, ears and joints. Cartilage tissue is composed of chondrocytes and a specific extracellular matrix that contains types II, IX, and XI collagen and proteoglycans, but not type I collagen. Cartilage tissue damaged by joint injury etc. does not spontaneously cure itself, and the damage will deteriorate without repair treatment such as transplantation. However, cartilage repair treatment suffers from the need to obtain cartilage tissue to be transplanted into the damaged area, and cartilage from other parts of the patient's body is not always sufficient in size for repair of the damage. The required in vitro expansion of harvested chondrocytes results in differentiation toward fibroblastic cells, which are not suitable for transplantation (Non Patent Literature 1). Another proposed treatment is the administration of mesenchymal stem cells. However, mesenchymal stem cells can differentiate into multiple cell types, and the administration results in transplantation of unsuitable tissue, such as fibrous tissue expressing type I collagen and hypertrophic tissue expressing type X collagen (Non Patent Literature 2).
Currently proposed is repair treatment using induced chondrocytes from pluripotent stem cells, such as iPS and ES cells (Non Patent Literature 3 to 7). However, several problems have arisen, including the formation of fibrocartilage and teratoma. Therefore, there is a need for the development of a method for driving pluripotent stem cells to generate high-quality cartilage tissue without in vivo cancer formation.